1. Field of the Invention
The invention relates to a vehicle control apparatus and a vehicle control method for a hybrid vehicle.
2. Description of the Related Art
Japanese Patent Laid-Open Publication No. 2000-324615 discloses a control apparatus for a hybrid vehicle, which drives an engine and a motor (that is used also as an electric generator) to enable the vehicle to run, and which starts the engine such that the electric generator generates electric power, and charges the battery with the generated electric power when a state of charge (SOC) of a battery is equal to or lower than a lower limit.
However, in a vehicle provided with the aforementioned control apparatus, when a load of the vehicle is large while the vehicle runs using only the driving force of the motor, a load of the battery is large, which may reduce a lifetime of the battery. When a load of a vehicle is large, for example, when a vehicle runs on an ascending slope, when a deadweight is large, when a freezer is operated in a refrigerated vehicle, or when a garbage collector is operated in a garbage collecting vehicle, the SOC of a battery is significantly reduced, a large amount of electric power is discharged from the battery and the battery is charged with a large amount of electric power, in a repeated manner. Accordingly, a temperature of the battery is increased by heat generation at a time of charge/discharge, which reduces the lifetime of the battery. In addition, when the SOC of the battery is reduced suddenly, a speed at which electric power is generated by the electric generator becomes lower than a speed at which the battery is requested to be charged, and the SOC of the battery may become lower than a permissible lower limit. In this case, the lifetime of the battery may be reduced as a result.